The chronic demyelinative myelopathy induced in mice by intracerebral inoculation of tissue culture cell-adapted DA virus is being studied under the light and electron microscopes, with particular attention to disease of anterior horn cells and of peripheral nerves. Motor end plates and peripheral mixed motor nerve tissues from ALS patients will be studied, searching for evidence of viral infection. The interaction of experimental allergic encephalomyelitis and infection with neurotropic strains of measles and herpes simplex type 2 viruses will be studied in rodents.